1. Field of the Invention
The present invention generally relates to hair removal, and in particular the invention relates to the use of ultrasonic energy to disrupt hair follicles to remove hairs and to prevent their regrowth.
2. Description of the Prior Art
Removal of unwanted hair from different parts of the body is a well established modality in cosmetic surgery practice as well as in cosmetology. It is performed by physicians and aestheticians. Methods currently used to perform this procedure include electrolysis, laser energy, non-laser pulsed light, tweezing, waxing and chemical depilation.
Electrolysis is the removal of unwanted hair by means of a needle inserted into the hair follicle, through which an electrical current or radio energy is passed.
The short wave or radio energy method of electrolysis, also known as the thermolysis or diathermy method, uses high frequency radio energy, which sets up a rapid oscillation or vibration in the cells of the follicle, producing heat. The resulting heat cauterizes the hair tissue. A few seconds are required to heat each hair; in high-speed "flash" thermolysis the current is applied for only a fraction of a second. In the galvanic method, the direct current passed through the needle produces sodium hydroxide in the follicle, which chemically acts to destroy the hair tissue. A minute or more is required for treatment of each hair follicle.
The blend method combines both the short wave and galvanic modalities and, with the oscillation of the high frequency radio energy, the sodium hydroxide produced in the follicle is heated and destroys the hair tissue. These methods may result in some discomfort. They are claimed to provide lasting results.
The laser energy method involves the use of a laser, which is pulsed or turned on for only a fraction of a second. The laser works by selectively targeting the melanin pigment inside the hair follicle. The duration of the pulses is adjusted so that the energy will be absorbed by the hair follicle and will disable it, but will not result in the transfer of excess heat to the surrounding skin. This method may employ a wide beam, so that many hairs can be treated at once.
In some laser processes a thin coat of a clear gel is applied to the skin before the laser pulses are applied. Other laser processes employ waxing before laser pulse application. The use of anesthesia may not be necessary. Most individuals experience a slight stinging sensation as the laser pulses are applied. Some parts of the body do tend to be more sensitive than others, and sometimes redness or swelling will occur for a few hours afterwards. Burning or scarring can result if the treatments are administered improperly. Hyperpigmentation or hypopigmentation may also result.
Laser methods produce lasting, but not permanent, results. They are among the most expensive methods of hair removal. Hair growth may be inhibited to some extent. A number of sessions may be required, depending on the part of the body being treated. The process removes visible hair and disables hair in the active or anagen phase. Follicles in the resting or telogen phase are not affected; additional sessions are required to treat these hairs as they enter the active phase. Treatment may prolong the telogen phase. The process is of limited effectiveness on light hair.
A variation of these methods makes use of a carbon lotion applied before exposure to laser light. Carbon particles in the lotion, rather than melanin, absorb the laser light.
The non-laser pulsed light method uses intense, pulsed light. In the dermis, light energy is converted to heat and absorbed by hair pigment to destroy the hair structures and impair hair regrowth. The skin is protected from thermal injury as it is allowed to cool between pulses of light while a high heat level is maintained in the hair follicle.
Treatment parameters can be customized to the particular body area, hair depth, hair color and skin type of the individual patient. The process is claimed to be effective at skin depths or 1 to 2 mm, greater than the depths at which laser processes can be used. The method has a much larger spot size than traditional laser technology, so it can cover the treatment area faster and in fewer sessions.
The non-laser pulsed light method offers long-lasting, but not permanent, results.
Waxing is a process in which a warm wax mixture (or, alternatively, a sugar mixture) is applied to the area to be treated, and spread in the same direction as hair growth. A cloth is then patted down onto the area, and removed quickly, after a few seconds, in the direction opposite to hair growth. The process is repeated until all the hair is removed. The area will remain free of hair for three to six weeks.
However, follicle and root are stressed and deformed in this process. As a result, the follicle can become distorted or curved, and an ingrown hair may result.
Tweezing or plucking is a process in which individual hairs are physically removed. It requires a great deal of time to treat even small areas, and can be painful. It is not recommended for large or more sensitive areas. As is the case with waxing, the process stresses the follicle and root. Distortion or curving of the follicle and an ingrown hair may result.
A variation on the tweezing method employs an epilator, a device using rotating disks to grab the hair and pluck it out. Hairs to be removed must be of a length sufficient for the epilator to grab them firmly. The process is less time-consuming than tweezing, but the pain level may be the same.
Another variation uses tweezing in conjunction with electrical current. Hair is not an electrical conductor, so it does not transmit current from tweezers to a hair bulb. Since the follicle is not exposed to electrical current, hair removal is not permanent.
Chemical depilation is carried out by applying a depilatory cream and allowing sufficient time for the cream to act on the hair. The cream and hair are removed, razor fashion, with a spatula and the skin is rinsed and wiped to remove any remaining material. The method works best on large areas. It is temporary, removing hair for a slightly longer period of time than shaving. It may cause problems to users with sensitive skin.
Ultrasonic tools are widely used in surgical practice for applications other than the removal of hair. They are used in neurosurgery, cataract removal, and the removal of tissue. Most of the instruments used in these applications have a distal tip which undergoes longitudinal or transverse vibrations when subjected to ultrasonic energy. The distal end may be either solid or have a linear aspirating passage to facilitate the removal of unwanted tissue debris.
Typically, the ultrasonic devices operate at 23 kHz, 37 kHz, or 40 kHz. Typical power output ranges between 20 and 100 watts.
Consequently, a need remains for a permanent method of hair removal in which burns and scarring are avoided, and which targets the hair follicle while not resulting in damage to other anatomic structures.